The present invent1on relates to a contact arrangement for low-voltage circuit breakers having main contacts for carrying a continuous current and burn-off contacts for igniting a switching arc in the entrance area of an arc quenching chamber and having arcing horns for transferring the switching arc into the arc quenching chamber, and wherein at least two main contacts are arranged in a row next to each other and at a distance therefrom at least one burn-off contact is arranged.
A contact arrangement of this kind has become known, for instance, from DE-A No. 2,218,420. Such contact arrangements are customarily chosen for transmitting a large current for an extended period of time with the smallest possible temperature rise of the contact arrangement. In principle, this is achieved by the provision that the main contacts work without an arc and are therefore not subjected to burn-off which could affect the contact surfaces adversely.
If such a contact arrangement is opened for switching off, the currents which initially flowed through the main contact are commutated to the burn-off contact so that only the latter are acted upon by the switching arc.
However, it is known that under certain conditions, especially if the contact arrangement is overloaded by very large currents, partial arcs can occur at the main contact even if the latter are opened before the burn-off contacts. To control such phenomena without danger to the contact arrangement, it is known to design the quenching baffles of the associated are quenching chamber widened in such a manner that entrance edges of the baffles are arranged opposite not only the burn-off contacts but also the main contacts (DE-A No. 2,218,420). This design of the quenching baffles, however, necessitates that the arc quenching chamber has the same width as the contact arrangement. With a multiplicity of interruption processes, this large volume of the arc quenching chamber would not be necessary, however, since only an arc occurring at the burn-off contacts needs to be transferred into the quenching chamber.